What Causes Light And Short Periods Along With Lower Back Pain?

I am 2 weeks late on my period and on the 5th day I had brown discharge and brown bleeding but stopped and only lasted that one day but still not come onto my period I also have bloating but don t know wether this was down to me also suffering from ibs I have had a test and says I m not pregnant I also suffered for 1 day too lower back pain and one side of my leg numb which has now gone can u give me some advise plz thx u